This invention relates to a fibrous product that is used in acoustical and decorative applications. More particularly, the invention relates to a dual density fibrous having good shape retention qualities and well-defined corners and edges. One application of the invention is directed to the use of this dual density fibrous product to make ceiling tiles that can be supported by the grid work that is normally associated with a suspended ceiling. This dual density fibrous material can also be used to make acoustical panels for use on the walls of a building.
Fibrous material has been used for a number of years to form acoustical and thermal products. The fibrous material is normally webs or batts of fibrous glass. However, other fibrous material such as mineral, organic or inorganic fibers can be used. Such fibrous material can be cut or molded to the desired shape to be used in the finished product. However, the fibrous material does not possess much rigidity or strength unless the fibers are compacted into a dense product. Such a dense product significantly increases the weight of the fibrous material and also reduces the thermal insulating characteristics of the fibrous material. A low density fibrous material has an acceptable weight and the desired thermal insulating characteristics but it is difficult to form sharp edges or corners in such a lower density fibrous product. In addition, the corners and edges in such a lower density product are frequently damaged during shipping, handling and actual use of such as product. Further, it is difficult to position a decorative surface, such as a fabric, on a lower density product as there is too much give and flexibility in the fibrous material to adequately bond the decorative material to the fibrous material. The positioning of the decorative material on the lower density fibrous material can also deform the configuration of the fibrous material.
A ceiling tile that is used in a suspended ceiling arrangement is a good example of a fibrous product wherein the above described limitations are extremely important. Such a ceiling tile is suspended around its outer periphery by a metal grid work that is suspended from the ceiling. Only a small portion of the outer periphery of the ceiling tile actually engages the metal grid work. Accordingly, there must be enough strength and rigidity in the outer periphery of the ceiling tile to support the ceiling tile without any sagging or structural failure. At the same time the ceiling tile should be light in weight so as not to place to great of a load on the support grid work and to reduce the load that the ceiling tile places on the outer periphery of the tile that engages the metal grid work. The ceiling tile should also have good thermal and acoustical characteristics that allow it to reduce the noise level and heat transmission level in the room where it is positioned. Such a ceiling tile should also be capable of accepting decorative surface coverings to enhance the appearance of the ceiling tile. Such covering should be firmly bonded to the fibrous material of the ceiling tile and it is particularly desirable to have sharp, well-defined edges and corners that will maintain their shape during handling, installation and use of the ceiling tiles.
From the above it is clear that it would be desirable to use a high denisty fibrous material to form such a ceiling tile so that the outer periphery of the ceiling tile would have sufficient strength to adequately support the ceiling tile in the suspended ceiling support grid. However, using a high density product significantly increases the weight of the ceiling tile and places undue loads on the support grid work. Such a high density product also greatly increases the cost of the ceiling tile and makes it much less cost competitive in the marketplace. A high density fibrous material also reduces the thermal insulating properties of the ceiling tile which is undesirable. At the same time the use of a low density fibrous material does not provide adequate strength to support the ceiling tile without the possibility of sagging or structural failure of the ceiling tile. In addition, such a low density fibrous material does not have the requisite physical integrity to form sharp, well-defined edges and corners and to maintain this appearance during actual use of the ceiling tile.
To remedy the above-discussed difficulties and limitations the manufacturers of ceiling tile normally select a fibrous material having a density that is compromised between the desirable properties of a high density product and the desirable properties of a low density product. Such a intermediate density product does not have the strength and appearance characteristics that are desirable and also does not exhibit the desired thermal characteristics. Such an intermediate density product also is not as light and cost efficient as the use of a lower density product.
In view of the above-enumerated shortcomings and difficulties, it is clear that there is a need in the marketplace for a fibrous product that can be used in such applications as ceiling tile that exhibits the characteristics of a high density product and the characteristics of a low density product. Such a product would be particularly suitable for use in ceiling tile, acoustical panels and other applications where decorative fibrous products having acoustical and thermal characteristics have been used in the past.